Yes, but an external glibc puts extra constraints on the nvidia driver versions I can use. The driver I have now works fine.

I see how that's a problem.

I know that GPU stuff is an area that requires some impurity on foreign Linux with Nix. I didn't realize that had implications for libc versions. :(

It wouldn't be a problem if it was easy to recompile the entire Nix system with a different glibc version.

To change glibc do you have to override the stdenv? Why is that hard? Do you have to make a new bootstrap or something awful like that?